KR102460331B1 - coated cutting tools - Google Patents

Abstract

The present invention relates to a coated cutting tool having a cemented carbide substrate comprising WC, a metallic binder phase and a gamma phase, wherein the cemented carbide has a well dispersed gamma phase, and the cemented carbide has a reduced amount of abnormal WC grains. Further, the coated cutting tool has a CVD coating comprising TiCN and a layer of α-Al ₂ O ₃ , wherein the layer of α-Al ₂ O ₃ exhibits a tissue modulus TC(0 0 12) ≥ 7.2, and a ratio I(0 0 12)/I(0 1 14) is ≥ 1. The coated cutting tool according to the present invention has increased resistance to plastic deformation while maintaining toughness.

Description

coated cutting tools

The present invention relates to a coated cutting tool for the chirp machining of metals comprising substrates and coatings, wherein the coated turning inserts are particularly suitable for machining steel.

Cutting tools having a cemented carbide substrate having a gamma phase-depleted binder phase rich surface area with a CVD coating are well known in the art of turning operations.

However, there is always an ongoing effort to improve the performance of cutting tools such as inserts. Longer tool life leads to lower production costs, etc.

Plastic deformation is one of the wear mechanisms in cutting operations. In general, when it is desired to improve resistance to plastic deformation, the toughness of the substrate is reduced.

It is an object of the present invention to achieve improved resistance to plastic deformation while maintaining toughness.

Another object of the present invention is to achieve improved resistance to plastic deformation while at the same time improving toughness.

The present invention relates to a coated cutting tool comprising a cemented carbide substrate and a coating. The cemented carbide substrate includes WC, a cobalt binder phase and a gamma phase, and the cemented carbide substrate includes a binder phase-rich surface region depleted of gamma phase, wherein the thickness of the surface region is 14 to 26 μm, and the cemented carbide substrate has an N of 80 has a well-dispersed gamma phase to be less than μm ² , wherein

where X (μm ² ) is the particle area (x-axis) at a cumulative relative area (y-axis) of 0.90 in the cumulative plot obtained from the EBSD analysis, where the cumulative relative particle area (y) of the gamma phase particles -axis) is plotted against particle area (x-axis).

Y is the correction factor

, where the area fraction is obtained from EBSD analysis.

Furthermore,

The area fraction of the abnormal WC grains obtained from the EBSD analysis defined as 0 ~ 0.03.

the coating comprises a layer of α-Al ₂ O ₃ , between the substrate and the layer of α-Al ₂ O ₃ the coating comprises a layer of TiCN, and the layer of α-Al ₂ O ₃ is prepared by Harris formula

denote the tissue modulus TC(hkl) as measured by X-ray diffraction using CuKα radiation and θ-2θ scans defined according to area), and I ₀ (hkl) is ICDD's PDF-card No. standard intensity according to 00-010-0173, n is the number of reflections used in the calculation, (hkl) reflections used are (1 0 4), (1 1 0), (1 1 3), (0 2 4), (1 1 6), (2 1 4), (3 0 0) and (0 0 12), TC(0 0 12) is ≥ 7.2, and I(0 0 12)/I(0 1 The ratio of 14) is ≥ 1.

The properties of the cemented carbide according to the present invention are performed using electron backscatter diffraction (EBSD). EBSD steps a beam across the sample surface by a defined distance (step size) and also determines the phase and crystallographic orientation of the sample at each step from the diffraction pattern generated when the sample is tilted 70° to the horizontal. SEM method. This information can be used to generate maps of the sample microstructure that can be easily evaluated using crystallographic information to determine the size and relative location of grain boundaries, phases, and grains.

The cemented carbide should have as few abnormal WC grains as possible. Abnormal WC grains generally refer to WC grains that are several times larger than the average WC grain size. The amount of abnormal WC grains herein is determined from EBSD analysis of cemented carbide material.

The area fraction of abnormal WC grains is defined as the area fraction of WC grains that, with respect to the total area of the WC grains, is greater than ten times the average area for WC grains (αWC _av ).

According to the present invention, the area fraction of the abnormal grains is 0 to 0.03, preferably 0 to 0.025, more preferably 0 to 0.02.

The gamma phase, which is a solid solution of cubic carbides and/or carbonitrides, is formed during sintering from cubic carbides and/or carbonitrides and WC, and can also be described as (W,M)C or (W,M)(C,N) wherein M is at least one of Ti, Ta, Nb, Hf, Zr, Cr, and V.

In one embodiment of the present invention, the cemented carbide comprises NbC in an amount of 0.5 to 2.5 wt %, preferably 1 to 1.5 wt %. Moreover, the cemented carbide contains TaC in an amount of 2.5 to 4.5 wt%, preferably 3 to 4 wt%. Furthermore, the cemented carbide contains TiC in an amount of 1.8 to 3.3 wt %, preferably 2 to 3 wt %.

The amount of the gamma phase is suitably 3 to 25 vol%, preferably 5 to 17 vol%. This can be measured in different ways, for example by image analysis of a micrograph of a scanning electron microscope (SEM) or an image of a light optical microscope (LOM) of a cross section of the substrate to calculate the average fraction of the gamma phase. When the cemented carbide has a gradient in the surface area, the amount of gamma phase as given herein is measured in bulk. The amount of gamma phase can also be retrieved from EBSD analysis.

The distribution of the gamma phase should be as uniform as possible. EBSD analysis of gamma phase was performed on gamma phase particles, not gamma phase grains. Through processing of the EBSD data, it is possible to choose whether to measure particles or grains. A grain is meant herein as a single crystal, whereas a particle means two or more grains in direct contact with each other.

According to the present invention, the gamma phase is well distributed with a controlled particle size.

The distribution of the gamma phase is determined by EBSD analysis and is also given by the value N:

The cumulative relative particle area (y-axis) of the gamma phase particles from the EBSD analysis is plotted against the particle area (x-axis). Reference is made to FIG. 1 . From the cumulative plot (0 to 1), the particle area (x-axis) at a cumulative relative area (y-axis) of 0.90, ie the value X (μm ² ) is achieved. If the value does not exactly match 0.90, the average of the two values less than and greater than 0.90 is used as X.

The value Y is a correction factor for correlating different amounts of gamma phase in cemented carbide. Y is a ratio obtained by dividing the area fraction of cubic carbide and cubic carbonitride (gamma phase) by the total amount of carbide and carbonitride, that is, WC (hexagonal crystal) and gamma phase (cubic crystal). Area fractions are obtained from EBSD data.

According to the invention, the gamma phase distribution, ie N, is suitably less than 80 μm ² , preferably 15 to 75 μm ² , more preferably 35 to 70 μm ² .

The thickness of the surface zone is suitably between 10 and 35 μm, preferably between 14 and 26 μm. The thickness is measured between the surface of the substrate and the boundary between the gamma-phase-depleted surface region and the gamma-phase-containing bulk. In SEM or LOM images, these boundaries are very distinct and therefore easy to identify. The measurement of the thickness of the surface area should preferably be made on a flat surface not too close to the cutting edge, preferably on the flank surface. It means here that the measurements have to be carried out at least 0.3 mm from the cutting edge.

Binder rich means herein that the binder phase content in the surface zone is at least 1.3 times the binder phase content in the bulk. The binder phase content in the surface zone is suitably measured at a depth of half the total thickness/depth of the surface zone. Bulk is defined herein as an area that is not a surface area. All measurements performed in bulk should be performed in an area that is not too close to the surface area. It means that any measurements made here on the microstructure of the bulk must be performed at a depth of at least 100 μm from the surface.

Depletion of gamma phase means herein that the surface region contains no gamma phase particles or very few gamma phase particles.

The amount of cobalt is 5 to 17 wt % of the sintered body, suitably 8 to 12 wt %.

In one embodiment of the present invention, when Cr is present in the cemented carbide, a part of Cr is dissolved in the binder phase.

The cemented carbide may also include other components common in the art of cemented carbide. When a recycled material (PRZ) is used, such Zr, V, Zn, Fe, Ni and Al may also be present in small amounts.

The coating according to the invention comprises an α-Al ₂ O ₃ layer, and between the substrate and the α-Al ₂ O ₃ layer the coating comprises a TiCN-layer. α-Al ₂ O ₃ is the Harris formula

denote the tissue modulus TC(hkl) as measured by X-ray diffraction using CuKα radiation and θ-2θ scans defined according to area), and I ₀ (hkl) is ICDD's PDF-card No. standard intensity according to 00-010-0173, n is the number of reflections used in the calculation, (hkl) reflections used are (1 0 4), (1 1 0), (1 1 3), (0 2 4), (1 1 6), (2 1 4), (3 0 0) and (0 0 12), TC(0 0 12) ≥ 7.2, preferably ≥ 7.4, more preferably ≥ 7.5, more preferably ≧7.6, most preferably ≧7.7, and preferably ≦8; The ratio of I(0 0 12)/I(0 1 14) is ≥ 1, preferably ≥ 1.5, more preferably ≥ 1.7, most preferably ≥ 2, and I(0 0 12) is 0 0 12 is the measured intensity (integral area) of the reflection, and I(0 1 14) is the measured intensity (integral area) of the 0 1 4 reflection. The α-Al ₂ O ₃ layer with such a high TC(0 0 12) in combination with I(0 0 12) greater than or equal to I(0 1 14) can be used in cutting tools due to its unexpectedly high crater and flank wear resistance. It has been shown to be advantageous as a layer.

The α-Al ₂ O ₃ layer is typically deposited by thermal CVD. HTCVD is defined herein as a CVD process within a temperature range of 950 to 1050 °C, and MTCVD is defined as a CVD process within a temperature range of 800 to 950 °C.

The α-Al ₂ O ₃ layer covers at least the area of the cutting tool that is engaged in cutting in a cutting operation and at least covers the areas exposed to crater wear and/or flank wear. Alternatively, the entire cutting tool may be coated with an α-Al ₂ O ₃ layer and/or any additional layers of coating.

Strong <0 0 1> texture here means statistically favorable growth along the <0 0 1> crystallographic direction, ie, α-Al ₂ O ₃ grains are more frequent than other crystallographic planes parallel to the substrate surface. It grows in a (0 0 1) crystallographic plane parallel to the substrate surface. <hk l> The means for expressing the desired growth along the crystallographic direction is the tissue coefficient TC ( hkl). The XRD reflection intensity is normalized using, for example, a JCPDF-card that shows the XRD reflection intensity of the same material, ie α-Al ₂ O ₃ , but with a random orientation in the material powder. The texture modulus TC (hkl) > 1 of the layer of crystalline material indicates that the grains of the crystalline material are at least parallel to the substrate surface and parallel to the substrate surface ( hkl) is an indication of orientation in the crystallographic plane. The tissue factor TC (0 0 12) is used herein to indicate the desired crystal growth along the <0 0 1> crystallographic direction. The (0 0 1) crystallographic plane is parallel to the (0 0 6) and (0 0 12) crystallographic planes in the α-Al ₂ O ₃ crystallographic system.

In one embodiment of the present invention, the thickness of the α-Al ₂ O ₃ layer is between 2 and 20 μm, preferably between 2 and 10 μm, most preferably between 3 and 7 μm.

The coating further comprises a TiCN layer, preferably MTCVD coated, located between the substrate and the α-Al ₂ O ₃ layer. The grains of the TiCN layer are columnar. In one embodiment of the present invention, the thickness of the TiCN layer is 4 to 20 μm, preferably 4 to 15 μm, and most preferably 5 to 12 μm. TiCN means Ti(C _x ,N _1-x ) herein, wherein 0.2≤x≤0.8, preferably 0.3≤x≤0.7, more preferably 0.4≤x≤0.6. The C/(C+N) ratio of TiCN can be measured, for example, by electron microprobe analysis.

The coating further comprises a bonding layer comprising TiN, TiCN, TiCNO and/or TiCO or a combination thereof, preferably TiCN and TiCNO, located on the outermost side of the TiCN layer and adjacent to the α-Al ₂ O ₃ layer . Preferably, the bonding layer is HTCVD deposited. The bonding layer is for strengthening the adhesion between the TiCN layer and the α-Al ₂ O ₃ layer. The bonding layer is preferably oxidized prior to deposition of the α-Al ₂ O ₃ layer. The thickness of the bonding layer is preferably 0.5 to 2 μm, most preferably 1 to 2 μm.

In one embodiment of the present invention, the TiCN layer positioned between the α-Al ₂ O ₃ layer and the substrate is measured by X-ray diffraction using CuKα radiation and θ-2θ scans defined according to Harris formula (1). denote the tissue coefficient TC(hkl) as defined, where I(hkl) is the measured intensity (integral area) of the (hkl) reflection, and I ₀ (hkl) is the ICDD's PDF-card No. standard intensity according to 42-1489, n is the number of reflections, and the reflections used in the calculation are (1 1 1), (2 0 0), (2 2 0), (3 1 1), (3 3 1 ), (4 2 0), (4 2 2) and (5 1 1), TC(2 2 0) is ≤ 0.5, preferably ≤ 0.3, more preferably ≤ 0.2, most preferably ≤ 0.1 to be. The low intensity from (2 2 0) was shown to be advantageous in that it appears to promote strong <0 0 1> organization of the subsequent α-Al ₂ O ₃ layer. One way to achieve low TC(2 2 0) is to adjust the volume ratio of TiCl ₄ /CH ₃ CN at the beginning, preferably at the beginning, of the MTCVD TiCN deposition to a relatively high level.

In one embodiment of the invention, the TiCN layer exhibits TC(4 2 2) ≥ 3, preferably ≥ 3.5. In one embodiment of the present invention, the TiCN layer exhibits TC(3 1 1) + TC(4 2 2) ≥ 4, preferably ≥ 5, more preferably ≥ 6, most preferably ≥ 7. These TC values are derived from Harris formula (1), ICDD's PDF-card no 42-1489 and reflections (1 1 1), (2 0 0), (2 2 0), (3 1 1), (3 3 1), It is calculated using (4 2 0), (4 2 2) and (5 1 1).

In one embodiment of the invention, the coated cutting tool is subjected to post-treatments customary in the art of coated cutting tools, such as blasting, brushing, etc.

A cutting tool means here an insert, preferably an insert for turning.

The coated cutting tool insert is suitably a turning insert for turning steel, cast iron or stainless steel.

1 shows a cumulative plot in which cumulative relative area (y-axis) is plotted against particle area (x-axis).

Example 1

Cemented carbide substrates are first pre-milled with recycled cemented carbide material (PRZ) with (Ta,Nb)C, (Ti,W)C and Ti(C,N) in a milling solution of ethanol and water (9 wt% of water) was manufactured by The ratio between powder and milling liquid was 232 kg of powder/80 L of milling liquid in a stirred mill called LMZ10 from Netzsch, a horizontal stirred mill in which the slurry is recirculated between the milling chamber and the holding tank. The slurry was milled at 650 rpm for an accumulated energy of 30 kWh.

PRZ, ie the amount of recycled material, is 20 wt % of the total powder weight. In Table 2, the composition in wt% for the PRZ used, batch number 828 is shown. The remaining raw materials are added in such an amount so that the composition of Table 1 is obtained.

After the pre-milling step, WC, Co powder and PEG (polyethylene glycol) were added to the slurry so as to be 800 kg of powder/160 L of milling liquid, and also the milling liquid was added to the slurry, and then all the powders were stirred at 650 rpm were milled together for an accumulated energy of 90 kWh.

The amount of PEG was 2 wt % of the total dry powder weight (PEG not included in the total dry powder weight).

The WC powder was hot carburized WC called HTWC040 purchased from Wolfram Bergbau und Hutten AG. The mean particle size (FSSS) after ASTM milling was 3.9 μm.

The slurry was then spray dried into agglomerates, which were then subjected to a pressing operation in a hydraulic press from a fette to form green bodies.

The green bodies were then sintered by first performing dewaxing in H ₂ at a maximum of 450 °C and vacuum heating to a maximum of 1350 °C. After that, a protective atmosphere of flowing 20 mbar of Ar and 20 mbar of CO is introduced, and then the temperature is maintained at 1450° C. for 1 hour.

The obtained cemented carbide is hereinafter referred to as Invention 1.

For comparison, the substrate was first prepared by the preparation of the cemented carbide substrate by milling all the raw powders in a conventional ball mill for 11 hours, ie, no pre-milling was performed.

The raw materials were the same as in Inventive 3, and 15 wt% of the total powder weight of the other PRZ batch (batch 757) was used (see Table 2), and a conventional having an average particle size (FSSS) after ASTM-milling of 7.0 μm. The difference is that WC (not high temperature carburizing) was used. Amounts of other raw materials are added in such amounts so that a composition according to Table 1 is achieved.

The obtained cemented carbide is hereinafter referred to as Comparative Example 1.

[Table 1]

[Table 2]

The remainder of the PRZ-powder (up to 100%) is traces of Fe, Ni and Al.

The slurry was then spray dried into agglomerates, which were then subjected to a pressing operation in a hydraulic press from a fette to form green bodies.

The materials achieved, i.e., Inventive 1 and Comparative Example 1, both had gamma-phase-depleted binder phase-rich surface regions with thicknesses of 22 and 23 μm, respectively.

The cemented carbide substrates were then provided with a coating. First, cemented carbide substrates were coated with a thin TiN-layer of approximately 0.4 μm by using the well-known MTCVD technique using TiCl ₄ , CH ₃ CN, N ₂ , HCl and H ₂ at 885° C., then approximately 7 μm was coated with a TiCN layer of In the initial part of the MTCVD deposition of the TiCN layer, the volume ratio of TiCl ₄ /CH ₃ CN was 6.6, followed by a cycle using a ratio of TiCl ₄ /CH ₃ CN of 3.7. Details of TiN and TiCN depositions are given in Table 3.

[Table 3] ( MTCVD of TiN and TiCN)

On top of the MTCVD TiCN layer, there was a 1-2 μm thick bonding layer deposited at 1000° C. by a process consisting of 4 separate reaction steps. First, the HTCVD TiCN step uses TiCl ₄ , CH ₄ , N ₂ , HCl and H ₂ at 400 mbar, then the second step (TiCNO-1) uses TiCl ₄ , CH ₃ CN, CO, N at 70 mbar ₂ and H ₂ , then the third step (TiCNO-2) uses TiCl ₄ , CH ₃ CN, CO, N ₂ and H ₂ at 70 mbar, and finally the fourth step (TiCNO-3 ) uses TiCl ₄ , CO, N ₂ and H ₂ at 70 mbar. During the third and fourth deposition phases, some of the gases were continuously changed as indicated by the first starting level and the second stopping level presented in Table 4. Before the start of subsequent Al ₂ O ₃ nucleation, the bonding layer was oxidized in a mixture of CO ₂ , CO, N ₂ and H ₂ for 4 min. Details of bonding layer deposition are given in Table 4.

[Table 4] (bonding layer deposition)

A layer of α-Al ₂ O ₃ was deposited on top of the bonding layer. All α-Al ₂ O ₃ layers were deposited in two steps at 1000° C. and 55 mbar. The first step uses 1.2 vol-% AlCl ₃ , 4.7 vol-% CO ₂ , 1.8 vol-% HCl and the remainder H ₂ to give about 0.1 μm of α-Al ₂ O ₃ , α-Al The second stage of the ₂ O ₃ layer was deposited using 1.2% AlCl ₃ , 4.7% CO ₂ , 2.9% HCl, 0.58% H ₂ S and the remainder H ₂ .

Example 2 (tissue analysis)

XRD was used to analyze the TC values of α-Al ₂ O ₃ and TiCN according to the method described above. The layer thickness was analyzed in light optical microscopy by studying the cross-section of each coating at 1000x magnification, and both the bonding layer and the initial TiN layer were contained within the TiCN layer thickness given in Table 5. In Table 5, a criterion (comparative example 1) which is commercial grade GC4235 is also included. Two samples of Invention 1 and Comparative Example 1 were respectively analyzed. The results are presented in Table 5.

[Table 5] (thickness and diffraction data)

Inserts according to the present invention were blasted against the rake face in wet blasting equipment using an alumina slurry in water, and the angle between the rake face of the cutting insert and the direction of the blaster slurry was about 90°. The alumina grits were F220, the pressure of the slurry to the gun was 1.8 bar, the pressure of the air to the gun was 2.2 bar, the average time to blast per unit area was 4.4 seconds, and the The distance to the surface was about 145 mm. The purpose of blasting is to influence the surface roughness and residual stresses in the coating, and thus to improve the properties of the inserts in subsequent turning tests.

Example 3 (microstructure)

The microstructure of the substrate was also analyzed by EBSD. Four images of 60*100 μm were used.

Inserts were prepared for electron backscatter diffraction (EBSD) characterization by an ion polished step performed on a Hitachi E3500 after polishing the cross section of the bulk material to a diamond size of 1 μm using mechanical polishing using diamond slurry.

The prepared sample was mounted on a sample holder and inserted into a scanning electron microscope (SEM). The samples were tilted towards the EBSD detector and at 70° relative to the horizontal plane. The SEM used for characterization was a Zeiss Supra 55 VP operating in high vacuum (HV) mode and using a 240 μm objective aperture applying “high current” mode. The EBSD detector used was an Oxford Instruments Nordlys detector operated using Oxford Instruments "AZtec" software version 3.1. EBSD data were obtained by applying a focused electron beam to the polished surface and sequentially acquiring the EBSD data using a step size of 0.1 μm for a measurement point of 1000×600 μm. When performing EBSD analysis for this purpose, the number of images should be chosen such that the total area from which EBSD data is obtained is at least 12000 μm ² .

SEM Settings

Acceleration voltage 20 kV

Aperture size 240 μm

High Current On

Working distance 8.5 mm

Detector insertion distance 171 mm

The reference phases were as follows:

WC (hexagonal), 59 reflectors, Acta Crystallogr., [ACCRA9], (1961), vol.14, pages 200-201

Co (cubic), 68 reflectors, Z. Angew. Phys., [ZAPHAX], (1967), vol. 23, pages 245-249

Co (hexagonal), 50 reflectors, Fiz. Met. Metalloved, [FMMTAK], (1968), vol. 26, pages 140-143

Cubic carbide phase, TiC, 77 reflectors, J. Matter. Chem. [JMACEP], (2001), vol. 11, pages 2335-2339

Since these cemented carbides contain two cubic phases, a Co binder phase and a gamma phase, care must be taken to ensure that the phases are correctly identified, ie the indexing is correct. This can be done in several ways, one method is to perform an EDS or backscatter image, on the same sample, which depends on the chemical composition of the phases and therefore the difference between the binder phase and the gamma phase for comparison. show

EBSD data were collected at AZtec by Oxford Instruments and also analyzed on HKL Channel5 (HKL Tango version 5.11.20201.0). Noise reduction was performed by removing wild spikes and performing zero solution extrapolation level 5. The WC grains were determined with a critical misorientation angle of 5 degrees. The grain boundaries between the gamma-phase grains were removed so that only the gamma-phase grains were analyzed. This was done by setting the critical direction deviation to 90 degrees on Channel 5. All particles less than 4 pixels (0.04 μm ² ) were removed as noise.

The distribution of the gamma phase is determined by EBSD analysis and is also given by the value N (μm ² ).

The cumulative relative particle area (y-axis) of the gamma phase particles from the EBSD analysis is plotted against the particle area (x-axis). From the cumulative plot, the particle area (x-axis) at a cumulative relative area (y-axis) of 0.90, ie the value X (μm ² ) is achieved. If the value does not exactly match 0.90, the average of the two values less than and greater than 0.90 is used as X.

The value Y is a correction factor for correlating different amounts of gamma phase in cemented carbide. Y is a ratio obtained by dividing the area fraction of cubic carbide and cubic carbonitride (gamma phase) by the total amount of carbide and carbonitride, that is, WC (hexagonal crystal) and gamma phase (cubic crystal). Area fractions are obtained from EBSD data:

The area fraction of abnormal WC grains is defined as the area fraction of WC grains that, with respect to the total area of the WC grains, is greater than ten times the average area for WC grains (αWC _av ).

For comparison, commercial grade GC4235 suitable for turning steel was also analyzed in the same way. GC4235 is referred to herein as Comparative Example 1.

The measurement results can be confirmed in Table 6 below.

In Table 6, the coercivity (Hc) and weight specific magnetic saturation magnetism are given.

Coercive force and weight specific magnetic saturation magnetic force were measured using a Foerster Koerzimat CS1.096.

[Table 6]

Example 4 (Operating Example)

Example 1 and inserts made according to invention 1 were tested together with comparative example 1 in a facing operation under dry conditions. The workpiece material was steel SS2541 with the following conditions:

Vc 160 m/min

f 0.3 mm/rev

a _p 2 mm

Based on tool life: Vb≥0.5 mm at main cutting edge

The results are presented in Table 7.

[Table 7]

As can be seen from Table 7, the insert according to the present invention exhibits improved resistance to plastic deformation of the cutting edge compared to the reference.

Example 5 (Operating Example)

The inserts disclosed in Example 1 and Inventive 1 were tested together with Comparative Example 1 in a turning operation under wet conditions. The workpiece is configured to have two intermittent occasions per revolution. The work piece was carbon steel SS1312 having the following conditions.

Vc 50 m/min

f 0.6 mm/rev

a _p 1.5 mm

Based on tool life: destruction without any other major wear

The results are presented in Table 8 below, and the tool life is an average of 8 tests.

[Table 8]

As can be seen from Table 8, the insert according to the present invention exhibits improved toughness behavior compared to the reference.

Claims (11)

A coated cutting tool comprising a cemented carbide substrate and a coating, comprising:
The cemented carbide substrate includes WC, a cobalt binder phase and a gamma phase, the cemented carbide substrate includes a binder phase rich surface region depleted of gamma phase, the thickness of the surface region is 14 to 26 μm, and the cemented carbide substrate has N has a well-dispersed gamma phase to be less than 80 μm ² ,

where X (μm ² ) is the particle area (x-axis) at a cumulative relative particle area (y-axis) of 0.90 in the cumulative plot obtained from EBSD analysis, and the cumulative relative particle area (y-axis) of gamma phase particles is plotted against the particle area (x-axis), the cumulative relative particle area (y-axis) means the ratio of the cumulative particle area to the particle area (x-axis) to the total particle area, , Y is the correction factor

, and the area fraction is obtained from EBSD analysis,

The area fraction obtained from EBSD analysis of abnormal WC grains defined as 0 ~ 0.03,
the coating comprises a layer of α-Al ₂ O ₃ , the coating between the substrate and the layer of α-Al ₂ O ₃ includes a layer of TiCN, and the layer of α-Al ₂ O ₃ has a Harris formula

Denote the tissue modulus TC(hkl) as measured by X-ray diffraction using CuKα radiation and θ-2θ scans defined according to
where I(hkl) is the measured intensity (integral area) of the (hkl) reflection, and I ₀ (hkl) is the ICDD's PDF-card No. standard intensity according to 00-010-0173, n is the number of reflections used in the calculation, (hkl) reflections used are (1 0 4), (1 1 0), (1 1 3), (0 2 4), (1 1 6), (2 1 4), (3 0 0) and (0 0 12),
TC(0 0 12) ≥ 7.2, or ≥ 7.4, or ≥ 7.5, or ≥ 7.6, or ≥ 7.7;
The coated cutting tool, wherein the ratio of I(0 0 12)/I(0 1 14) is ≥ 1, or ≥ 1.5, or ≥ 1.7, or ≥ 2. The method of claim 1,
wherein the amount of the gamma phase is 3-25 vol%. The method of claim 1,
The coated cutting tool, wherein the area fraction of the abnormal WC grains is 0 to 0.025. The method of claim 1,
The gamma phase distribution (N) is between 15 and 75 μm ² , the coated cutting tool. 5. The method according to any one of claims 1 to 4,
The thickness of the TiCN layer is 4-20 μm, the coated cutting tool. 5. The method according to any one of claims 1 to 4,
The α-Al ₂ O ₃ layer has a thickness of 2 to 20 μm, a coated cutting tool. 5. The method according to any one of claims 1 to 4,
wherein the coating further comprises a bonding layer comprising TiN, TiCN, TiCNO, TiCO, or a combination thereof, located on an outermost side of the TiCN layer and adjacent the α-Al ₂ O ₃ layer. 8. The method of claim 7,
The thickness of the bonding layer is 0.5 ~ 2 ㎛, coated cutting tool. 5. The method according to any one of claims 1 to 4,
The TiCN layer positioned between the α-Al ₂ O ₃ layer and the substrate had a tissue modulus TC (hkl) as measured by X-ray diffraction using CuKα radiation and θ-2θ scans defined according to the Harris formula. ), where I(hkl) is the measured intensity (integral area) of the (hkl) reflection, and I ₀ (hkl) is the ICDD's PDF-card No. standard intensity according to 42-1489, n is the number of reflections, and the reflections used in the calculation are (1 1 1), (2 0 0), (2 2 0), (3 1 1), (3 3 1 ), (4 2 0), (4 2 2) and (5 1 1),
TC(2 2 0) is ≤ 0.5, or ≤ 0.3, or ≤ 0.2, or ≤ 0.1. 10. The method of claim 9,
wherein the TiCN layer exhibits TC(4 2 2) ≥ 3, or ≥ 3.5. 10. The method of claim 9,
TC(3 1 1) + TC(4 2 2) of the TiCN layer is ≥ 4, or ≥ 5, or ≥ 6, or ≥ 7;

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